'Supermoon' larger, brighter, but size difference is difficult to see

One day before a supermoon, a commercial airliner crosses the waxing gibbous moon on its final approach to Los Angeles Airport as viewed from Whittier, Calif. on Friday, July 11, 2014. Photo Credit: AP / Nick Ut

But despite the hype, astronomers say it's almost impossible to perceive the difference with the naked eye.

"The only way you can tell the difference is . . . to take a photograph" and compare the supermoon with a full moon that is at its farthest from Earth, said Susan Rose, president of the Amateur Observers Society of New York.

The full effect of a supermoon -- technically known as a perigee-syzygy moon -- can elude even a practiced eye. The supermoon is anywhere from 7.2 percent to 17 percent bigger than the full moon at its farthest point from Earth, according to some estimates.

"To try and decide if it's 5 percent larger or smaller seems like a fool's errand," said Ken Spencer, a former Newsday photographer who is president of the Astronomical Society of Long Island. "Just go out and soak it in."

While Rose called the supermoon phenomenon a "media event," she said she hoped it would spur more people to get interested in what's beyond Earth.

"Anything that gets people to look into the sky to learn a little bit more about what's going on there is a good thing," she said.

The supermoon was responsible for a coastal flood advisory along Nassau County's South Shore on Sunday night, when the pull of the moon was expected to coincide with high tides to slosh water into basements and onto flood-prone streets.

The light of the supermoon may make the annual return of the Perseid meteor shower less visible.